This invention relates to the packaging of perishable products, particularly those products, such as meat, which are purchased fresh by the consumer and then preserved by home freezing.
Exposure of perishable products to the ordinary atmosphere results in spoilage, both from bacterial decay and, in the case of red meat, from the irreversible conversion of myoglobin meat pigment to the grey or brown metmyoglobin, which color change renders the meat unacceptable to the average consumer. However, if air circulation around the product is limited or excluded, other types of spoilage occur and meat loses its red color. This is because exposure to oxygen is desirable for meat, at temperatures above freezing, in order to oxygenate the meat pigment to bright red oxymyoglobin, which produces the red bloom which is desired by the average consumer.
It is known to package perishable products in an atmosphere which inhibits bacterial decay, such as carbon dioxide.
It is also known to package red meat in an atmosphere of pure or enriched oxygen, which favors the formation of oxymyoglobin over metmyoglobin, and in an atmosphere containing enriched oxygen and carbon dioxide, the latter to inhibit bacterial growth. Packaging may be designed to encourage maximum exposure of the surface of the packaged product to the modified atmosphere, thus significantly extending the shelf life of the product and reducing wastage through spoilage, both of which are advantages to the retailer.
It is increasingly common for the consumer to extend the life of perishable products bought fresh in packages from the supermarket or similar stores by home freezing. When such products are frozen, exposure to air or other gaseous atmosphere causes discoloration through dehydration, so-called "freezer burn". This renders the food less attractive and affects its quality. The packaging described above, which is designed to increase exposure to the atmosphere in the package, is therefore highly unsuitable for the purpose of freezing. If the consumer places such a package in a home freezer in the state in which it is purchased, frezer burn almost inevitably results. In order to avoid freezer burn, the consumer must completely repackage the food product at home, which is inconvenient. The result of these disadvantages has been that this type of packaging, while it reduces waste and is advantageous to the retailer, has not found general customer acceptance.